This application relates to a force sensor utilized in combination with an adjustment mechanism for a disc brake, wherein the force sensor provides an accurate indication of the point of brake application to a control associated with the adjustment mechanism.
Disc brakes have historically included a mechanical adjustment mechanism to adjust for wear. As known, in a disc brake, a brake actuator drives a pair of pistons, and the pistons force a brake pad against a rotor, slowing rotation of the rotor. There is normal wear on the brake pad, and typically the pistons are provided with the mechanical adjustment mechanism. The mechanical adjustment mechanism includes a mechanical linkage that senses the total movement, and adjusts the pistons relative to tappet gears to take up clearance. Typically, there is a desired amount of piston movement, and with wear on the brake pad, the pistons need to move an amount beyond this desired amount. Thus, the mechanical adjustment mechanism changes a rest, or starting position of the pistons such that they only need to move the desired amount, even with wear on the brake pad.
More recently, electric motors have been developed for replacing the mechanical linkage in the adjustment mechanism. An electric motor typically drives a gear, that in turn will drive the tappet gears to adjust the pistons.
Such electric motor adjustment mechanisms would desirably have an indication of when the brake first came into contact with the rotor, as this is an important measurement for determining an accurate amount of adjustment. However, to date, no practical application or location for placement of a force sensor has been identified in the disc brake environment. Strain gauges, etc. have been placed along the force transmission path, however, these are not practical in the environment of the disc brake actuation assembly. Typically, there is little available space along the transmission path.
Force sensors have also been proposed incorporated into the actuator. However, this location is somewhat remote and may not provide feedback as accurately as desired.